Syntheses, crystal structures, and magnetic properties of a series of cyanide-bridged trinuclear chromate(III)-nickel(II)-chromate(III) complexes based on dicyanidechromate(III) building blocks

摘要

Four cyanide-bridged trinuclear Cr~(III)-N~(III)-CrIII complexes [Ni(cyclam)][Cr(bpb)(CN)_2]_2·2H _2O (1) (cyclam = 1,4,8,11-tetraazacyclotetradecane, bpb2- = 1,2-bis(pyridine-2-carboxamido)-benzenate), [Ni(cyclam)] [Cr(bpClb)(CN) _2]_2·4H_2O (2) (bpClb~2- = 1,2-bis(pyridine-2-carboxamido)-4-chloro-benzenate), [Ni(cyclam)][Cr(bpmb)(CN) _2]_2·4H_2O (3) (bpmb~2- = 1,2-bis(pyridine-2-carboxamido)-4-methyl-benzenate) and [Ni(cyclam)][Cr(bpdmb) (CN)2]2 (4) (bpdmb2 = 1,2-bis(pyridine-2- carboxamido)-4,5- dimethyl-benzenate) have been synthesized by the reaction of [Ni(cyclam)](ClO_4)_2 with a series of dicyanidechromate(III) building blocks. Single crystal X-ray diffraction analyses show that the four complexes have similar trinuclear structures with Cr~(III)- C≡N-Ni~(II)-N≡C-Cr~(III) linkages. Magnetic investigations indicate the ferromagnetic coupling between Cr(III) and Ni(II) centers through the cyanide bridge, with JCrNi = 4.64(3) cm~(-1) for 1, 4.33(4) cm~(-1) for 2, 3.57(3) cm~(-1) for 3 and 5.3(1) cm ~(-1) for 4. The study on magneto- structural correlation for cyanide-bridged Cr~(III)-NiII systems reveals that the cyanide-bridging bond angle is related to the strength of magnetic exchange coupling: the larger the Ni-N≡Cbond angle, the stronger the Ni· · · ·Cr magnetic interaction.